Zusammenfassung
Synkopen stellen bei Patienten mit Long-QT-Syndrom (LQTS) eine differentialdiagnostische Herausforderung dar: einerseits könnte es sich um lebensbedrohliche Torsade-de-pointes-Tachykardien handeln, andererseits gerade im Adoleszentenalter auch um harmlose orthostatische Intoleranzreaktionen. In diesem Fallbericht wird die Anwendung der Impedanzkardiografie in Kombination mit nicht invasiver beat-to-beat Blutdruckmessung zur Abklärung einer Synkope geschildert. Dadurch konnte bei einer Patientin mit LQTS 2 (Mutation im HERG-Gen) während des Kipptischversuchs eine neurokardiogene Synkope vom gemischten Typ induziert werden. Von diagnostischer Bedeutung war hier vor allem der während der Kippphase im Verlauf abnehmende periphere Gefäßwiderstand in Verbindung mit dem reduzierten Herzzeitvolumen, der in eine Bradykardie mündete. Dies wurde als Ursache für die Synkope angesehen, zumal der Zusammenhang zwischen neurokardiogener Synkope und Long-QT-Syndrom in zwei Studien belegt worden ist. Zusätzliche, nicht invasive Untersuchungen zeigten keinen Hinweis auf eine maligne Arrhythmie. Die Versuchsanordnung eröffnete in diesem Fall eine ergänzende, nicht invasive diagnostische Möglichkeit. Inwieweit die bei der demonstrierten Indikationsstellung wertvolle Versuchsanordnung auch auf andere Krankheitsbilder übertragen werden kann, muss im Einzelfall entschieden werden; sicherlich ergeben sich aber neue Einblicke in die Regulation der Orthostase im Kindesalter.
Summary
Syncope represents a diagnostic challenge in patients affected by long-QT syndrome (LQTS). It is crucial for the therapeutic decision to distinguish between potentially life-threatening ventricular tachycardias (Torsadede-pointes) and—especially during adolescence—neurocardiogenic syncopes. This case report presents a patient with LQTS2 (mutation in the HERG gene) on medication with beta-blocker, in whom a head-up-tilt table test was performed after syncope of unknown origin. The test was chosen in order to reproduce the circumstances under which the syncope had happened. The monitoring device consisted of impedance cardiography as well as non-invasive beat-to-beat blood-pressure measurement. By these means it was possible to register a reduced peripheral vascular resistance after tilting the patient, a reduced cardiac output and bradycardia leading to syncope after four minutes of upright posture. This was suggestive for neurocardiogenic syncope as a cause for the spell experienced. Further non-invasive diagnostic methods were normal. As the patient’s family history was negative for syncopes, Torsade-de-pointes seemed unlikely.
In this special case the non-invasive monitoring system of cardiac output, peripheral vascular resistance and beat-to-beat blood pressure measurements was useful as a supplemental tool during evaluation of syncope and helpful in decision-making against implantation of an ICD and for a more intense treatment with betablockers. Such monitoring devices offer new insights into the orthostatic regulation in young patients.
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Dalla Pozza, R., Kleinmann, A., Bechtold, S. et al. Impedance cardiography and beat-to-beat blood pressure monitoring in diagnosis of syncope in long-QT syndrome. ZS Kardiologie 94, 767–771 (2005). https://doi.org/10.1007/s00392-005-0290-6
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DOI: https://doi.org/10.1007/s00392-005-0290-6